In recent years, diagnosis or treatment of a lesion or a stenosis is performed by inserting a catheter into a blood vessel or the like of a patient (for example, PCI (Percutaneous Coronary Intervention) or TAE (Transcatheter Arterial Embolization)).
During the diagnosis or treatment, a surgeon manipulates the catheter while monitoring an X-ray fluoroscopic image of a tip end of the catheter. At this time, the surgeon needs to accurately grasp the direction of the tip end of the catheter in order to align, at a branching portion of the blood vessel, the direction of the tip end of the catheter with the branching direction of a target blood vessel.
As a conventional technique for detecting the direction of a catheter, a method of detecting the rotation angle of the catheter at the hand of the surgeon is disclosed (see Patent Literature 1). Also, a method of mounting a rotation detection sensor at a tip end portion of an electronic endoscope, and automatically correcting a display image on a monitor obtained with a twist in the electronic endoscope is disclosed (see Patent Literature 2).